Whatever 10% of 1000 is lol... That will be in the third level
It would have trouble breathing because the partial pressure of oxygen at that elevation is lower than the partial pressure of oxygen at sea level.
Hope that helped you.
An isotonic solution refers to two solutions having the same osmotic pressure across a semipermeable membrane. This state allows for the free movement of water across the membrane without changing the concentration of solutes on either side.